ToXchange There is no shortage of concerning headlines these days when it comes to environmental health and human exposures and frequently the public is left with more confusion rather than clarity as it tries to understand complex science and who to turn to for accurate, objective, science-based information.
Whether the issue is lead in children’s toys, melamine in milk, or bisphenol A in plastics, at the end of the day, the consumer wants to know the relevance for them and whether there is a reason to be concerned or not. At issue is the often challenging job of trying to understand how reported scientific studies relate to human health and risk. The following can be of help in deciphering complex and often contentious science and what it means for humans. When evaluating a toxicology study or perhaps a collection of studies, some of the first questions to be asked are:
- Has the study been reproduced and validated or is this a one-time reporting event—in other words, what is the weight of scientific evidence for a particular claim and has consistency in effect been reported over time?
- Was the study conducted in experimental animals, cell cultures, or is the study based on human evidence? If one of the first two and if there is no human evidence to lend credibility to reported claims, then this needs to be taken into account when evaluating the potential relevance to humans.
- If a toxicology study was conducted in experimental animals or in other test systems, how do the dose levels used compare to actual or predicted human exposures? Frequently, because toxicologists are interested in defining a dose-response relationship, they use experimental doses that are hundreds to thousands of time above expected human exposures or environmental concentrations and this needs to be considered when evaluating relevance to humans.
- Another key variable that offers insight on relevance to humans is the route of exposure that was used in the study of interest in other words, did the study employ one of the 3 basic ways by which humans could be exposed—orally, dermally, or through inhalation, or were novel approaches such as intravenous (IV) or subcutaneous (injection under the skin) routes of administration used?
Consumers need to understand that risk is composed of two key variables—hazard and exposure—and some element of each has to be present for a risk to exist. Frequently the public hears only about the potential hazard associated with a chemical, natural toxin, or other agent with no information about expected or actual human exposures. Every time that a newspaper article, a TV report, or an internet posting claims a new health risk to humans, consumers need to be vigilant and ask how the reported exposures relate to actual human exposure. This helps to place the study or report into proper context and helps to more accurately define the risk or provide reassurance to concerned humans.
In summary, when faced with uncertain and confusing science, many times involving toxicology studies, one needs to ask how consistent and credible the studies are, in what test systems the studies were employed, how exposure was administered and how the doses or concentrations relate to actual human exposures. By asking these few, but important questions, consumers can advantage themselves and know that they are using sound scientific approaches to understanding risk in their world.